The objective of the proposed research is to increase our understanding of the way nervous systems are organized, by relating the network properties of a group of neurons to the physiology of the synaptic junctions which interconnect them. Synaptic neurobiology and interneuronal organization will be correlated by examining the buccal ganglia of the marine mollusc Aplysia californica. This preparation contains a reference population of 26 cells, including 4 multi-action interneurons, which is analyzable at the level of the individual indentified neuron, of the synaptic connections between individual identified cells, and of the cell networks formed by identified synapses. Electroanatomical identification of additional neurons, simultaneous intracellular recordings from pre- and post-synaptic elements, and voltage-clamping of postsynaptic potentials may yield answers to such questions as: How is a neural network anatomically specialized to function as two parallel channels? Can a neuron inhibit itself? How are cells specialized to aid co-ordination of bilateral activity? What factors determine the time course of conductance changes underlying a CNS postsynaptic potential? The principles of organization of identified cell networks in this preparation may prove applicable to experimentally less accessible populations of vertebrate neurons.